Pope Francis has called for solidarity with migrants, praising those who shelter them, during his traditional Christmas Day message.

"Our support should not be lacking to all those who flee extreme poverty or war, traveling all too often in inhumane conditions and not infrequently at the risk of their lives," he said, speaking from the central balcony of St. Peter’s Basilica in Rome.

"May God repay all those, both individuals and states, who generously work to provide assistance and welcome to the numerous migrants and refugees," the pontiff added.

Earlier this week, the UN refugee agency and the International Organization for Migration said that more than one million refugees and migrants arrived by land and sea in the European Union this year, while a further 3,600 died or went missing.

During his Urbi et Orbi (to the city and to the world) address, the pontiff also expressed his support for UN efforts to end the conflicts in Syria and Libya.

The Pope, who was addressing thousands of pilgrims, also condemned "brutal acts of terrorism," singling out deadly attacks in France, Lebanon, Egypt, Tunisia, and Mali.

He also renewed calls for peace in the Middle East, Africa, and other conflict-stricken regions.

The Pope urged Israelis and Palestinians to resume direct peace talks, and back international efforts to end "atrocities" in Libya and Syria.

Such acts, he said, "do not even spare the historical and cultural patrimony of entire peoples," a reference to the Islamic State militant group, which has seized large swaths of Syria and neighboring Iraq.

He also mentioned the conflicts in Ukraine, Colombia, Yemen, Iraq, Burundi, South Sudan, and the Democratic Republic of Congo.

As has been the case since the deadly Paris attacks carried out by Islamist militants last month. heavy security was in place around the Vatican as crowds lined the streets.